| Based on my years of working experience,according to the construction requirements of the storage tank and the production plan of the oil depot,the newly built storage tank may be put into operation in winter,or it may be put into operation after winter.Due to maintenance and other reasons,empty tanks may overwinter in service.In northeast China,the huge change of ambient temperature may have a negative impact on the storage tank body,especially the safety and reliability of the storage tank foundation.Therefore,it is necessary to evaluate and analyze the safety of the storage tank in the case of overwintering empty tank,and clarify the influencing factors of the safety of the overwintering empty tanks.On the basis of summing up the winter climate characteristics in the cold region,this paper analyzes the influence of low temperature,sudden temperature drop and foundation soil frost heave on the empty storage tank.In order to quantify the change of temperature environment on the stress of no-load storage tank,the finite element method is used to establish the finite element model of the storage tank.Based on the structural strength of the tank,the stress field of the key parts of the storage tank body is calculated under the ambient temperature of 0℃,-15℃,-30℃,-45℃ and-60℃;Using the same method,the maximum stress of the key parts of the tank body is calculated under the condition that the temperature drops suddenly by 10℃,15℃,20℃ and 25℃ within 24 hours,and finally the impact of low temperature environmental conditions and temperature changes on the safety of the tank structure is determined.The criteria for frost heaving of tank foundation soil are given,and the displacements of 20mm,30mm,34mm and 35mm are applied to calculate the stress distribution of tank body after frost heaving of foundation soil,determine the frost heaving limit value of foundation soil,and study the safety guarantee measures for no-load overwintering of tank.The empirical results show that the maximum stresses of the middle plate,edge plate,first ring wall plate and manhole of the no-load storage tank are less than the allowable stresses in the cold region of Northeast China under the low temperature environment and sudden temperature drop.Therefore,the overwintering of the no-load storage tank will not cause damage to the tank structure.For low temperature environment may cause foundation frost heave,when the local deformation of the tank body does not exceed 34mm,the whole tank will also be safe;When the local deformation of the tank body exceeds 34mm,the stress of the bottom plate exceeds the allowable stress,and the bottom plate will undergo plastic deformation.With the increase of deformation,the bottom plate will be damaged.At this time,the stress of the wall plate is very small,and the main damage occurs at the edge plate of the tank bottom.Based on this,it is proposed that perlite and other insulation materials can be laid on the bottom plate of the empty tank to increase the protection of the tank bottom foundation.In order to verify the thermal insulation effect of perlite,at the end of the paper,the finite element model is used to evaluate the thermal insulation results of perlite with different thickness in the low temperature environment.The evaluation results show that laying 5-10cm perlite on the bottom plate of the empty tank is the best thickness for thermal insulation effect and economic investment. |
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